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<p>在接触runtime前，团队开发时为便于调试，常常需要在model里进行description重写，手工重写十分的繁琐不便。而通过runtime方法交换可以无需一行代码即可自定义description，十分方便。另外，从服务器请求下来的json数据包含中文，控制无法直接显示中文，通过重写<br>DescriptionWithLocale方法Uinicode转码后可以方便查看中文，方便开发调试。</p>
<p>需导入<code>#import &lt;objc/runtime.h&gt;</code></p>
<ol>
<li>description—-当通过NSLog函数打印一个对象时，其输出结果就是该对象的description方法的返回值</li>
<li>debugDescription—当在LLDB中，通过诸如po命令打印一个对象时，其输出结果就是该对象的debugDescription方法的返回值。</li>
<li>debugDescription—默认实现就是直接返回description方法的返回值。</li>
</ol>
<p>代码如下：</p>
<figure class="highlight objectivec"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#import <span class="string">&quot;NSObject+AutoDescription.h&quot;</span></span></span><br><span class="line"><span class="meta">#import <span class="string">&quot;NSObject+Propertys.h&quot;</span></span></span><br><span class="line"><span class="meta">#import <span class="string">&lt;objc/runtime.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> 1.description----当通过NSLog函数打印一个对象时，其输出结果就是该对象的description方法的返回值</span></span><br><span class="line"><span class="comment"> 2.debugDescription---当在LLDB中，通过诸如po命令打印一个对象时，其输出结果就是该对象的debugDescription方法的返回值。</span></span><br><span class="line"><span class="comment"> 3.debugDescription---默认实现就是直接返回description方法的返回值。</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">@implementation</span> <span class="title">NSObject</span> (<span class="title">AutoDescription</span>)</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> *  C 方法交换</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">static</span> <span class="type">void</span>  SwizzleMethods_AutoDes(Class cls, SEL originalSel, SEL newSel)</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">//获取实例方法</span></span><br><span class="line">    Method originalMethod = class_getInstanceMethod(cls, originalSel);</span><br><span class="line">    Method newMethod = class_getInstanceMethod(cls, newSel);</span><br><span class="line">    <span class="comment">//改变两个方法的具体指针指向</span></span><br><span class="line">    method_exchangeImplementations(originalMethod, newMethod);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="comment">// DEBUG输出</span></span><br><span class="line"><span class="meta">#<span class="keyword">ifdef</span> DEBUG</span></span><br><span class="line">+ (<span class="type">void</span>)load &#123;</span><br><span class="line">    <span class="keyword">static</span> <span class="built_in">dispatch_once_t</span> onceToken;</span><br><span class="line">    <span class="built_in">dispatch_once</span>(&amp;onceToken, ^&#123;</span><br><span class="line">        SwizzleMethods_AutoDes([<span class="built_in">NSObject</span> <span class="keyword">class</span>], <span class="keyword">@selector</span>(description), <span class="keyword">@selector</span>(autoDescription));</span><br><span class="line"><span class="comment">//        method_exchangeImplementations(class_getInstanceMethod([NSObject class], @selector(description)), class_getInstanceMethod([NSObject class], @selector(autoDescription)));</span></span><br><span class="line">    &#125;);</span><br><span class="line">&#125;</span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">- (<span class="built_in">NSString</span> *)autoDescription</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">if</span> (![<span class="keyword">self</span> isKindOfClass:[<span class="built_in">NSObject</span> <span class="keyword">class</span>]]) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">nil</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 调试状态</span></span><br><span class="line">    <span class="built_in">NSArray</span> * allProperties = [<span class="keyword">self</span>  getAllProperties];</span><br><span class="line">    <span class="built_in">NSString</span> * print_str = [<span class="built_in">NSString</span> stringWithFormat:<span class="string">@&quot;❗%@\n&quot;</span>,[<span class="keyword">self</span> <span class="keyword">class</span>]];</span><br><span class="line">    <span class="keyword">for</span> (<span class="built_in">NSString</span> * propertyName <span class="keyword">in</span> allProperties) &#123;</span><br><span class="line">        <span class="type">id</span> value = [<span class="keyword">self</span> valueForKey:propertyName]?:<span class="string">@&quot;nil&quot;</span>;<span class="comment">//默认值为nil字符串</span></span><br><span class="line">        <span class="keyword">if</span> (![value isKindOfClass:[<span class="built_in">NSString</span> <span class="keyword">class</span>]]) &#123;</span><br><span class="line">            <span class="keyword">return</span> print_str;</span><br><span class="line">        &#125;</span><br><span class="line">        print_str = [print_str stringByAppendingFormat:<span class="string">@&quot;\t└%@:%@\n&quot;</span>,propertyName,value];</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> print_str;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>


<p>Uicode转码方法<br>参考 <a target="_blank" rel="noopener" href="http://stackoverflow.com/questions/2099349/using-objectivec-cocoa-to-unescape-unicode-characters-ie-u1234/">StackFlow</a></p>
<figure class="highlight objectivec"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">+ (<span class="built_in">NSString</span> *)stringByReplaceUnicode:(<span class="built_in">NSString</span> *)string</span><br><span class="line">&#123;</span><br><span class="line">    <span class="built_in">NSMutableString</span> *convertedString = [string mutableCopy];</span><br><span class="line">    [convertedString replaceOccurrencesOfString:<span class="string">@&quot;\\U&quot;</span> withString:<span class="string">@&quot;\\u&quot;</span> options:<span class="number">0</span> range:<span class="built_in">NSMakeRange</span>(<span class="number">0</span>, convertedString.length)];</span><br><span class="line">    <span class="built_in">CFStringRef</span> transform = <span class="built_in">CFSTR</span>(<span class="string">&quot;Any-Hex/Java&quot;</span>);</span><br><span class="line">    <span class="built_in">CFStringTransform</span>((__bridge <span class="built_in">CFMutableStringRef</span>)convertedString, <span class="literal">NULL</span>, transform, <span class="literal">YES</span>);</span><br><span class="line">    <span class="keyword">return</span> convertedString;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">@end</span></span><br></pre></td></tr></table></figure>

<p>字典NSDictionary，数组NSArray Description</p>
<figure class="highlight objectivec"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">pragma</span> mark--- NSDictionary Description</span></span><br><span class="line"><span class="meta">#<span class="keyword">if</span> DEBUG</span></span><br><span class="line"><span class="comment">//直接打印中文乱码问题</span></span><br><span class="line"><span class="comment">//http://objccn.io/issue-9-1/</span></span><br><span class="line"><span class="class"><span class="keyword">@implementation</span> <span class="title">NSDictionary</span> (<span class="title">AutoDescription</span>)</span></span><br><span class="line"></span><br><span class="line">+ (<span class="type">void</span>)load</span><br><span class="line">&#123;</span><br><span class="line">    SwizzleMethods_AutoDes([<span class="built_in">NSDictionary</span> <span class="keyword">class</span>], <span class="keyword">@selector</span>(descriptionWithLocale:), <span class="keyword">@selector</span>(autoDescriptionWithLocale:));</span><br><span class="line">    SwizzleMethods_AutoDes([<span class="built_in">NSDictionary</span> <span class="keyword">class</span>], <span class="keyword">@selector</span>(descriptionWithLocale:indent:), <span class="keyword">@selector</span>(autoDescriptionWithLocale:indent:));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">- (<span class="built_in">NSString</span> *)autoDescriptionWithLocale:(<span class="type">id</span>)locale</span><br><span class="line">&#123;</span><br><span class="line">    <span class="built_in">NSString</span> *description=[<span class="keyword">self</span> autoDescriptionWithLocale:locale];</span><br><span class="line">    <span class="keyword">return</span> [<span class="built_in">NSObject</span> stringByReplaceUnicode:description];</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">- (<span class="built_in">NSString</span> *)autoDescriptionWithLocale:(<span class="type">id</span>)locale indent:(<span class="built_in">NSUInteger</span>)level</span><br><span class="line">&#123;</span><br><span class="line">    <span class="built_in">NSString</span> *description=[<span class="keyword">self</span> autoDescriptionWithLocale:locale indent:level];</span><br><span class="line">    <span class="keyword">return</span> [<span class="built_in">NSObject</span> stringByReplaceUnicode:description];</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">@end</span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">pragma</span> mark--- NSArray Description</span></span><br><span class="line"><span class="class"><span class="keyword">@implementation</span> <span class="title">NSArray</span> (<span class="title">AutoDescription</span>)</span></span><br><span class="line"></span><br><span class="line">+ (<span class="type">void</span>)load</span><br><span class="line">&#123;</span><br><span class="line">    SwizzleMethods_AutoDes([<span class="built_in">NSArray</span> <span class="keyword">class</span>], <span class="keyword">@selector</span>(descriptionWithLocale:), <span class="keyword">@selector</span>(autoDescriptionWithLocale:));</span><br><span class="line">    SwizzleMethods_AutoDes([<span class="built_in">NSArray</span> <span class="keyword">class</span>], <span class="keyword">@selector</span>(descriptionWithLocale:indent:), <span class="keyword">@selector</span>(autoDescriptionWithLocale:indent:));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">- (<span class="built_in">NSString</span> *)autoDescriptionWithLocale:(<span class="type">id</span>)locale</span><br><span class="line">&#123;</span><br><span class="line">    <span class="built_in">NSString</span> *description=[<span class="keyword">self</span> autoDescriptionWithLocale:locale];</span><br><span class="line">    <span class="keyword">return</span> [<span class="built_in">NSObject</span> stringByReplaceUnicode:description];</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">- (<span class="built_in">NSString</span> *)autoDescriptionWithLocale:(<span class="type">id</span>)locale indent:(<span class="built_in">NSUInteger</span>)level</span><br><span class="line">&#123;</span><br><span class="line">    <span class="built_in">NSString</span> *description=[<span class="keyword">self</span> autoDescriptionWithLocale:locale indent:level];</span><br><span class="line">    <span class="keyword">return</span> [<span class="built_in">NSObject</span> stringByReplaceUnicode:description];</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">@end</span></span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line"></span><br></pre></td></tr></table></figure></div></article><div class="post-copyright"><div class="post-copyright__author"><span 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